A New Safety and Stability Enhanced Riser Control System: An Integrated Hybrid Riser Tensioning System

This paper presents the framework for a novel riser tensioning system using a hybrid arrangement for energy management. This hybrid tensioning system, which integrates electrical tensioners and energy storage elements with existing hydro-pneumatic tensioners, is designed to enhance the safety of a deepwater riser system by improving stability and dynamic performance. Four control modes are investigated for the framework implementation: 1. Normal operation mode for active heave compensation. 2. Riser-recoil mode to control recoil on sudden release and minimize unwanted riser upward movement. 3. VIV suppression mode to reduce disturbances induced by ocean currents in the riser string and to extend riser fatigue life. 4. Reconnection mode provides control to allow reconnecting the LMRP to the BOP without using the drawworks, freeing the drawworks from the time consuming procedure of landing the LMRP and tensioning the riser. A replacement strategy is proposed so that one can update any existing system to the hybrid riser tensioning system by replacing certain pairs of hydro-pneumatic tensioners with the novel electrical riser tensioners to achieve smooth system upgrade and better system reliability.